Among the joining methods used to assemble aircraft structures made of composite materials, preferably Carbon Fiber Reinforced Plastic (CFRP), metallic materials or hybrid combinations of them, are well known riveting methods using short threaded rivets with a sliding adjustment such as the HI-LITE rivets manufactured by Hi Shear Corporation.
These rivets, developed exclusively for the aerospace industry, consist of a threaded pin whose head may be protruding or countersunk and a nut or collar which limits the torque applied by breaking a part of it. In the case of closed structures such as fuselages, which must use a large number of rivets to join the fuselage skin with the various internal stiffening elements (frames, stringers, beams), the installation of collars on pins previously inserted from the outside of the fuselage is usually carried out manually with the aid of a pneumatic tool.
The riveting process includes the following basic steps:
Operators are distributed in random areas for working in parallel. The order of collar installation is not important.
Each operator is provided with the collars that he will need (pre-deposited in separate boxes for each reference).
For each specific pin, the corresponding collar is selected, a manual threading operation of the collar on the pin with a ½-¾ turn is done and, using a pneumatic or electric tool, the complete fastening of the collar is done until a part of it breaks.
Finally, the broken part of the collar is manually extracted from the pneumatic or electric tool, with a jolt.
The head of the pneumatic or electric tool is relatively simple and therefore small in size. It consists of a central hexagonal pin which remains in a fixed position and blocks the rotation of the pin, and a socket through which it applies torque to the hexagonal head collar. Once it reaches the torque corresponding to the breaking point of the collar employed, the detached body part or surplus remains lodged in the socket. A slight jolt is enough to detach it. This process is laborious and has the disadvantage of being highly labor intensive, increasing the cost of the aircraft manufacture. Additionally the operators sometimes have to adopt non-ergonomic positions for the collar installation operations.
The present invention is directed to solving these problems.